U.S. Pat. No. 5,079,247 to Tomcufcik et al. describes a process for preparing certain substituted benz[cd]indol-2-(1H)-imines starting from a compound having a preformed benz[cd]indol-2-(1H)-one ring structure with an unsubstituted amino group and a carboxyl group. The starting material is treated with an alkyl halide to obtain a 1-substituted benz[cd]indol-2-(1H)-one, and then reacted with phosphorus pentasulfide to convert the oxygen atom of the carboxyl group to a sulfur atom, giving a 1-substituted benz[cd]indol-2-(1H)-thione. The sulfur atom is then displaced with an amine compound, forming the substituted benz[cd]indol-2-(1H)-imine.
Similarly, U.S. Pat. No. 4,261,896 to Tomcufcik et al. discloses a process where a substituted benz[cd]indole-2-(1H)-one is treated with an alkyl halide to give a 1-substituted benz[cd]indole-2-(1H)-one, which is treated with phosphorus pentasulfide to give a 1-substituted benz[cd]indol-2-(1H)-thione, which in turn is treated with an amine compound to give the substituted benz[cd]indol-2-(1H)-imine. In both of the above processes of Tomcufcik et al., a compound having a fully formed tricyclic nucleus is used as the starting material.
Other processes for preparing various compounds from certain preformed tricyclic ring systems are also known. For example, U.S. Pat. No. 3,853,911 to Schefczik and U.S. Pat. No. 5,039,820 to Kress et al. disclose processes where tricyclic compounds are alkylated. U.S. Pat. No. 3,004,975 to Grob et al. and Australian Patent No. 229,221 describe the manufacture of hydrogenated benz[cd]indoles from 2-oxo compounds, such as 8-amino-1,2,3,4-tetrahydro-naphthalene-1-carboxylic acid lactams. U.S. Pat. No. 4,683,313 to Laguzza et al., U.S. Pat. No. 4,369,188 to Sestanj, British Patent Publication No. 791,804, European Patent Publication No. 0 392 768 A1, and Bowman et al., "1,3,4,5-Tetrahydrobenz[cd]indoles and Related Compounds. Part III," J. C. S. Perkin I, 1973, 438-442, pertain to processes of making benz[cd]indole compounds from a tricyclic material.
U.S. Pat. No. 5,026,869 to Flaugh also discloses two reaction schemes for preparing certain benz[cd]indole compounds, namely 6-substituted-4-dialkylaminotetrahydrobenz[cd]indoles. One reaction scheme, like those described above, starts with a tricyclic compound. A second reaction scheme goes through a tricyclic intermediate, which is prepared from a bicyclic starting material having a 5-membered ring and a 6-membered ring.
Such known processes suffer from various drawbacks and disadvantages, however, such as the requirement of a preformed tricyclic lactam ring or the use of inconvenient starting materials or reaction schemes.